Added some tests for json.writer, fixed a bug with t >json and json-null >json

basis/json/writer/writer-tests.factor

@@ -0,0 +1,18 @@
+USING: json.writer tools.test multiline json.reader ;
+IN: json.writer.tests
+
+{ "false" } [ f >json ] unit-test
+{ "true" } [ t >json ] unit-test
+{ "null" } [ json-null >json ] unit-test
+{ "0" } [ 0 >json ] unit-test
+{ "102" } [ 102 >json ] unit-test
+{ "-102" } [ -102 >json ] unit-test
+{ "102.0" } [ 102.0 >json ] unit-test
+{ "102.5" } [ 102.5 >json ] unit-test
+
+{ "[1,\"two\",3.0]" } [ { 1 "two" 3.0 } >json ] unit-test
+{ <" {"US$":1.0,"EU€":1.5}"> } [ H{ { "US$" 1.0 } { "EU€" 1.5 } } >json ] unit-test
+
+! Random symbols are written simply as strings
+SYMBOL: testSymbol
+{ <" "testSymbol""> } [ testSymbol >json ] unit-test

basis/json/writer/writer.factor

@@ -2,7 +2,7 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: kernel io.streams.string io strings splitting sequences
 math math.parser assocs classes words namespaces make
-prettyprint hashtables mirrors tr ;
+prettyprint hashtables mirrors tr json.reader ;
 IN: json.writer
 
 #! Writes the object out to a stream in JSON format
@@ -15,6 +15,9 @@ GENERIC: json-print ( obj -- )
 M: f json-print ( f -- )
   drop "false" write ;
 
+M: t json-print ( t -- )
+  drop "true" write
+
 M: string json-print ( obj -- )
   CHAR: " write1 "\"" split "\\\"" join CHAR: \r swap remove "\n" split "\\r\\n" join write CHAR: " write1 ;
 
@@ -41,4 +44,4 @@ M: hashtable json-print ( hashtable -- )
   CHAR: } write1 ;
 
 M: object json-print ( object -- )
-    unparse json-print ;
+    dup json-null = [ "null" write drop ] [ unparse json-print ] if ;